All product development is aimed in principle at reducing production costs and at achieving a higher-quality product. This applies to a very great extent to products of the hearing protection type. An analysis of the hearing protections currently available on the market shows that all the products follow certain common design solutions. It can be stated, for example, that all hearing protections of the cup type comprise two cups, each with a washer which extends around its opening and which is intended to support a sealing and comfort ring intended to rest against the head. The cups are either mounted in a frame or in separate holders intended to be fitted on a safety helmet.
Each cup and washer is produced by injection-molding of suitable plastic material in the form of two separate components, which are joined together in a later assembly step. They can be joined together in different ways, e.g. by adhesive bonding, ultrasound welding, or using snap-fit connections. The use of two production steps and a special assembly step results in higher production costs than would be the case if the production could take place in a single step, and it can result in a faulty product with poor fit between washer and cup, which can lead, for example, to sound getting through.
However, in a hearing protection cup of the abovementioned type, the washer intended for the sealing and comfort ring generally projects inward across the opening, from its edge formed by the shell of the cup. This means that the hollow space in the cup under the washer cannot be formed with a conventional insert since the latter, after a molding operation, cannot be removed again from the tool.